CVE-2021-24002Public exploitNetwork attack vector

Arbitrary FTP command execution via encoded newlines

Published Jun 24, 2021 · Updated Aug 3, 2024

Improper input neutralization in Mozilla Firefox, Firefox ESR, and Thunderbird before their fixed versions allows remote attackers to execute arbitrary FTP commands via a clicked FTP URL. FTP URL parsing interpreted percent-encoded carriage-return and line-feed characters as command separators, injecting attacker-chosen commands into the FTP control connection. Exploitation requires a user to click the crafted link and access to an FTP server; the resulting commands can modify or delete server data.

CVSS severity8.8
High
EPSS probability1.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input neutralization in Mozilla Firefox, Firefox ESR, and Thunderbird before their fixed versions allows remote attackers to execute arbitrary FTP commands via a clicked FTP URL. FTP URL parsing interpreted percent-encoded carriage-return and line-feed characters as command separators, injecting attacker-chosen commands into the FTP control connection. Exploitation requires a user to click the crafted link and access to an FTP server; the resulting commands can modify or delete server data.

The record

CVE
CVE-2021-24002
Published
Jun 24, 2021
Updated
Aug 3, 2024
Vendor
Mozilla
Product
Firefox
Classifications
CWE-74, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 24, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <88

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <88
Mozilla · Thunderbirdversion=unspecified <78.10
Mozilla · Firefox ESRversion=unspecified <78.10

Published CVSS scores

8.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8NVDAV:N/AC:M/Au:N/C:P/I:P/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-74Improper Neutralization of Special Elements in Output Used by a Downstream Component (Injection)
T1203Exploitation for Client Execution

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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